Mauritius is a volcanic island formed some 8 to 12 million years ago during the Miocene age and forms part of a vast submerged oceanic volcanic chain, the Mascarene Ridge that includes the Mascarene Islands of Rodrigues, Mauritius and Reunion which lie at its southern end. It has been estimated that the volcanic activity on Mauritius continued until as recently as 100,000 years ago and is still active on the younger island of Reunion.

The Mascarene Ridge is a spectacular extinct volcanic plateau of submerged shallow banks dominating the western Indian Ocean. It extends approximately 2,000 km between Seychelles (a remnant of the super-continent Gondwanaland – not volcanic) and Mauritius, covering an area of 115,000 km2 of shallow water banks with depths ranging from 8 m to 150 m on the plateaux, plunging to abyssal depths of 4000 m at its edges. These Banks comprise three main areas. To the south the small archipelago of St Brandon (Cargados Carajos), north of which the larger fully submerged Nazereth and the Saya de Malha Banks can be found. Almost spanning the entire tropical South West Indian Ocean, extending form close to the Equator in the north to close to the Tropic of Capricorn in the south, the Mascarene Ridge is larger than the Great Barrier Reef and longer than the Red Sea, and is one of the few submerged features clearly visible from space.

The predominant movement of water and weather crosses this region is in a north westerly direction, towards the East African coast. It is indisputable that this vast submarine ridge has a profound effect on the ocean currents and deep water mixing processes in the region, bringing nutrients and cold water to the surface and possibly influencing regional and global weather patterns. It is probable that the Mascarene Ridge also plays an important role in the bio-geographical distribution of important marine biodiversity and resources throughout the region as water is forced over and through the Ridge.

However, surprisingly little is known or has been published about the Mascarene Ridge, yet it represents an area where a number of oceanic and physical processes can be studied in close proximity, an interface between deep and shallow waters away from the influence of major land masses and their associated impacts. It is in fact a massive natural marine/atmospheric laboratory.


The island was formed in three distinct phases. The first phase was the emergence of the island from below the sea by massive volcanic eruption. The second and third phases combined high volcanic activity followed by erosion, during which time the northern plains and the northern shelf islets of Gunners Quoin, Flat, Gabriel Islands, Round and Serpent islands were formed. At this time the sea levels were 100 m lower and these northern islets formed part of the northern plain system.

Mauritius is 58 km from north to south and 47 km from east to west with an area of 1865 km2. The other island dependencies of Mauritius include, Rodrigues 600 km to the east, St Brandon (Cargados Carajos) 460 km to north east and Agalega 1200 km to the north. Reunion lies approximately 220 km and Madagascar 800 km to the west of Mauritius.

The topography of the island consists of a central plateau which rises dramatically to the south west with the highest point being Piton de la Petite Riviere Noire at 828 m. The central plateau is surrounded by the remnants of the primary volcanic crater system, including the second highest pint of Pieter Both at 823 m (the one with the boulder on top). To the north the island drops and flattens out to form the extensive northern plains extending down the west coast of the island as a coastal plain. The east coast has a very narrow to non existent coastal plain with relatively steep topography rising from the coast.

The longest river on the island is the Grand Riviere Sud Est which is 34 km from its head waters in the central plateau to where it enters the sea near Ile aux Cerfs.

Formation of the Coral Reef in Mauritius
In Mauritius corals started to grow in shallow waters parallel to the shore resulting in the formation of a fringing reef, covering 150 Km around the coast of Mauritius. In the south east, at Grand Port/Mahebourg, there is a short stretch of typical barrier reef, while there are no reefs on the south coast. In geological terms a fringing reef is a relatively young reef. Fringing reefs protect the shoreline and the coral and seagrass habitats that develop within the lagoon. Reefs are very complex with different shaped corals forming ecological niches.

36 Genera and 90 species of hard corals have been recorded in the waters of Mauritius. Growth rates of coral colonies vary from 0.5 cm – 7 cm per annum and a football size coral head takes approximately 50 years or more to grow. As the coral colonies grow, the remaining skeletal forms of the organisms consolidate forming coral bedrock that is the foundation of the reef. The growth rate of a reef platform is dependent on environmental factors, but it is generally accepted to be around 1 cm per year. However corals are fragile and can be easily impacted and broken. As the living structure of the reef platform is broken down by trampling, pollution, or other impacts, the height of the reef platform is lowered exposing the lagoon habitats and the shoreline to excessive wave action which they are not designed to withstand, often contributing to shoreline erosion.

Impacts on the lagoon and coral reefs of Mauritius
The impacts on the lagoons and coral reefs of Mauritius have been chronic and intense, starting 400 hundred years ago with the demise of the native forests, resulting in chronic sedimentation in the lagoons. Massive clearing of land for sugar plantations brought with it further sedimentation and associated pesticides and fertilisers being washed into the lagoons. The filling in of what were extensive wetlands which act as important natural filters has had severe impacts on the lagoons with polluted run off water directly entering the lagoon. Sand extraction for the construction industry caused more sedimentation and erosion of the seagrass beds. Excessive sedimentation results in poor light quality, inhibiting coral growth and can also smother the coral, killing the colonies. Uncontrolled coastal and industrial development with associated pollution, dynamite fishing and other negative forms of fishing such as the seine nets have all contributed as long term stressors on the lagoons and reef systems.

Tourism also has its direct and associated impacts, with snorkel and dive boats dropping anchors and breaking the coral, collection of shells and corals for sale to visitors has depleted the number of shells and people holding, walking and sitting on coral all contribute to the demise of the lagoon habitats the visitors have come to see.

Today, many of these impacts are being addressed. Sand extraction is no longer legal, although it still goes on. Pollution controls are being put in place including urban sewage systems and there are laws governing coastal development, new construction must be stepped back a stipulated distance from the high water mark and not exceed two stories – however it is not always clear in all cases that these regulations are being enforced. It is illegal to collect coral and shells in Mauritius, but it is legal to import from elsewhere, making it impossible to enforce the local law and merely displaces the problem from Mauritius to other countries such as Madagascar, Philippines and Indonesia. Dynamite fishing no longer takes place and the placing of Fixed Mooring Buoys on popular dive sites and (eventually) snorkel sites will protect corals from anchor damage, but there is still work to do to ensure that the tourism industry does not continue to destroy the very habitats that it is so dependent on.

The Days of the DODO
For the Dutch seamen under Van Warwyck in 1598, Mauritius was a paradise. A first description of Mauritius in 1598 based on this expedition was published in 1601. Quoting the descriptions from this book gives a clear indication of how the island was; ‘the country is mountainous and is covered with green forests of mostly wild trees, in the midst of which there are palm trees. The soil is rocky everywhere; it is covered with trees that grow so closely together that one can hardly move between them. The wood of those trees is of the finest ebony ever seen, as black as tar and may be polished like ivory….There is another type of wood, dark red in colour and yet another which is yellow as wax. There is a large quantity of palm trees which have provided the fleet with excellent refreshment. The head after being cut reveals a sort of marrow inside that is white and soft as a turnip but brittle – it is eaten raw and can be prepared as a salad’. This is likely one of the first descriptions of the Palm Heart salad.

‘The sea was so full of fish that, at first try, with the men using the large fishing net, half a ton were captured, so much so that it was difficult for the net to be pulled back as it was so full of fish. Those species of fish not be found in the United Provinces except the eels and perches. A ray was captured that was quite sufficient to provide two meals for the entire crew of one ship.

We found many tortoises, some of which were so big that four sailors could stand on each of them while they kept moving about. Their shells were so large that six men could sit on each of them. There are so many birds, including a large number of turtle-doves, that the sailors killed up to 150 in one afternoon, and if they could have carried back even more with them, they would have taken by hand or by using sticks as many as they would have wanted. There were also many herons, but it was impossible to approach them. There was a small number of wild geese and also many grey parrots. In addition there were birds which were as large as swans. Each of them had a large head on which a patch of skin formed a sort of hood; they had no wings, in the place of which were four to five black feathers, and for a tail, they had four or five curled greyish feathers’
. This was the description of the dodo.

The word Dodo is believed to be of Portuguese origin – doudo meaning stupid or foolish in Portuguese, probably reflecting the opinion that the Portuguese seamen had of the bird that by all accounts was particularly easy to catch. By reputation, it was apparently a fatty bird with a foul taste. Despite its apparent bad taste, (the Dutch called the dodo Walg-vogel, the ‘distasteful bird’) the Dutch continued to kill the bird in large numbers, salting them for stores and eating the small portions such as the stomach and gizzard that were considered to be tasty, discarding the rest of the bird. Only some years after the first recorded contact with man, the dodo was extinct, famous for the rather dubious honour of being the first recorded species in what has become a long line of species to suffer extinction. However, it has been speculated that it was the introduction of the pigs, rats and cats that brought about the final demise of the dodo, not necessarily direct over exploitation by man.

Already by 1601 large numbers of rats had been noted by passing voyagers and yet the island was not settled by the Dutch until 1638. Such an influx of invasive species such as rats, cats and pigs must have had massive yet unrecorded impacts on the natural biodiversity of the island – perhaps the dodo was only the tip of the iceberg.


There are no distinct monsoon periods in Mauritius. The weather is dominated by the southeast trade winds and it can rain any day of the year. The rainfall is heavier on the south eastern mountain slopes and central plateau with annual averages varying from 1000 mm in Flic en Flac to 6000 mm in the midlands on the central plateau. The east coast tends to be drier than the west coast, but is more exposed to the prevailing southeast winds. The coolest winter months are from July to September when temperatures can be as low as 24o C during the day and as low as 16o C during the night with 6o C being the lowest recorded minimum. The hottest months are from January – April with temperatures ranging from 25 – 35o C with periods of very high humidity.

The summer months are also the cyclone season. Cyclones passing near Mauritius can have a serious effect on the local weather with heavy rains and squally winds even if the cyclone does not make a direct hit on the island. Direct hits only occur every few years, but this may be a changing scenario. Cyclones bring heavy rains, strong winds and are not to be messed with. No one goes to sea. There are 4 levels of cyclone warnings issued by the Meteorological office.

Cyclone Warning Levels
• Class 1: Cyclone in the vicinity but posing little risk for the moment.
• Class 2: Schools are closed, but offices and shops continue as usual. Expect an increase in the wind speed possibly more rain and stock up on provisions.
• Class 3: Every one heads for home to batten down the hatches. The cyclone is not necessarily a direct hit but will be close enough to experience winds in excess of 100 kph. Electricity and telephones will probably be cut off. Bulletins are announced on the MBC radio station 94.7 every half hour. Winds are strong and gusty with heavy rain
• Class 4: The cyclone is a direct hit on the island. Stay indoors. Winds in excess of 120 kph with torrential rain. Electricity and telephone probably cut off during class 3 water may be cut off during Class 4, but the radio will continue to give valuable updates on the progress of the storm.

Essential equipment apart from food and water include a good torch, a transistor radio with sufficient batteries for both, gas cooker with spare gas cannister, paraffin or gas lights, candles, cloth or newspapers to mop up the inevitable leaks, set freezer to maximum so as to preserve frozen goods as long as possible after the electricity has been cut, books and or games.

Listed below are some of the details about some of the Cyclones that have hit Mauritius and Rodrigues courtesy of the Mauritius Meteorological Website and Sydney Selvon, A history of Mauritius 2001.

Date Name WIND KPH BAR HPa Place recorded & Comments
Apr 1892 1892 240 947.0 Port Louis, 1100 people killed, greatest loss of life by cyclone in Mauritius
Mar 1931 No Record
Feb 1945 1945 150 969.0 Pleasance
Jan 1960 Alix 200 970.0 Medine
Feb 1960 Carol 256–300 943.0 Medine, 40 people killed 80,000 homeless
Feb 1962 Jenny 235 995.2 Fort William
Apr 1962 Maud 205 955.0 Pointe Canon, Rodrigues
Feb 1963 Grace 203 980.0 Medine
Dec 1967 Carmen 213 978.0 Medine
Mar 1968 Monica 277 933 Marechal
Feb 1972 Fabienne 254 967.4 Marechal
Feb 1973 Jessy 220 962.9 Marechal
Feb 1975 Gervais 280 950.9 Alma, 9 people killed
Dec 1979 Claudette 221 964.0 Plaisance
Feb 1994 Hollanda 216 984.0 Fort William
Jan 2002 Dina 228 988.0 Le Morne
Feb 2003 Gerry 143 986.3 Fort William
Mar 2003 Kalunde 211 963.8 Plain Corail, Rodrigues

It should be noted that cyclones were named in alphabetic order, so for example Kalunde was the eleventh cyclone to have been recorded and monitored in the area.